Study Of Steam Huff And Puff To Steam Flooding In Extra Heavy Oil Reservoir Of XingⅡ And XingⅢ In Block Du 84

XingⅡ and XingⅢ oil layer of Xinglongtai reservoir in block Du 84 are extra heavy oil reservoir with medium thickness interbedded lithologic structure,which are characterized by moderate buried depth,simple structure,good physical properties and weak heterogeneity.At present,the average round of steam huff and puff exploitation have reached more than 15 times,and the recovery rate has exceeded 40%.It has entered the late stage of steam huff and puff,and the economic benefits have become worse.Convert development mode is the inevitable choice to improve the economic benefit and recovery degree of this reservoir and realize high-quality development.This paper is based on the analysis of reservoir geological characteristics,the study of huff and puff development status and effect evaluation,by comparing with the successful cases of steam huff and puff to steam flooding in similar reservoir(block Du229),the laboratory experimental research and field pilot test,it is considered that the development of extra heavy oil reservoir in Xing Ⅱ and Xing Ⅲ oil layer in Du 84 block needs to meet three conditions: First,the reservoir temperature is above 90℃,and the crude oil has flowing ability under reservoir conditions;Second,the reservoir pressure is lower than 5MPa,which is conducive to the improvement of steam thermal efficiency;Third,thermal communication should be formed between oil layers of injectionproduction wells.The present reservoir geological conditions and development status meet the conditions of alternative flooding,and alternative flooding development is feasible.Based on this,this paper determines the key technical and economic index of steam flooding,such as the economic limit production of single well group,the economic limit thickness of steam flooding reservoir,the economic limit oil-gas ratio of alternative flooding production,the well spacing of steam flooding pattern and the opportunity of alternative steam flooding,and optimizes the key operating parameters of steam flooding by using numerical simulation and reservoir engineering method: the bottom hole dryness is greater than 50%,the steam injection rate is 1.8 t/d ha m,and the production-injection ratio is 1.2.According to the research result,116 steam flooding well groups are optimized for xingⅡ and xing III oil layer in block Du84.Numerical simulation predicts12 years of single well group steam drive production,and improves recovery by 19.1%.